It's not just about inflation, agents, and general greed, but also that many clubs have learned to sell well. The conditional Renato Sanchez is not worth 40 million, he is 18 and he is only promising. But Bayern are buying it for 40. Why? Because Bayern can buy it for 40 and close the deal without fear of competitors. The fact is, among other things, big clubs have to pay extra for players. And they willingly do it, because I know that sooner or later they will beat off the money. And since big clubs overpay, the price tags go up. Because if you have a store of pretentious tweets for rich ladies, then you can put any price tags, knowing that ladies will not count money.
First, this is due to inflation. Many transfers, which in the nineties and zero were made for 10-15 million, now would have become more expensive one and a half times (the same Zidane would have cost Real Madrid not 46 million, but about 71 (sports.ru data)).
Secondly, football is now not just a game, it has been "commercialized", and a footballer is now not only a player, but also an asset that can be earned by selling T-shirts with his name, to raise the fans' interest in the campaign to the stadium, etc. All this brings money to the club and popularity of the brand, and, accordingly, the more famous the player, the more money and popularity the club will have in the future.
There are many more factors that affect the price tag of a football player, such as:
1) the prospects of his development and his talent (they often pay for the future, in the hope that a player with great potential will grow into a top-level footballer)
2) player's uniform according to the season
3) time remaining until the expiration of the player's contract with the club
4) the growing role of football agents lately, who may demand a percentage of the transfer to their own account (here, of course, Mino Raiola should be highlighted)
5) And, of course, the banal appearance of billionaire owners from clubs willing to invest they have large sums and pay a lot of money for players
The arrival of big money in the form of American, Arab and Chinese investors, firstly, the time of large fees for TV rights and record advertising contracts, secondly
Club reluctance to let go of its player;
Or when your player is interested in the money bag;
Also, clubs can spread rumors in the newspapers to "gain prices".
In general, now only two were bought for that kind of money - Bale for 101 and Pogba for 105. The closest figures are Ronaldo for 94 and Higuain for 90.